Detailed introduction to the principle of Redis implementing flash sales in PHP

With the popularization of the Internet and people's pursuit of convenient life, more and more e-commerce platforms and services have begun to launch flash sales activities. Flash sales not only attract many users, but also become an important means of promotion for e-commerce platforms. How to ensure the stability and fairness of flash sale activities is a problem that e-commerce platforms have always faced. In this context, the method of using Redis to implement flash sales in PHP has gradually become a popular solution. This article will introduce in detail the principle, process and issues that need to be paid attention to when Redis implements flash sales in PHP.

1. Introduction to Redis

Redis is an open source in-memory database with the characteristics of high performance, high availability, and high concurrency. The data structures of Redis include strings, hashes, lists, sets, ordered sets, etc., and the data types that can be stored are very rich. Redis also supports publish and subscribe, transactions, Lua scripts and other functions.

In the flash sale event, Redis serves as a cache database, which can improve the system's reading and writing speed while ensuring the reliability of the data. Redis uses a single-threaded method to operate, reducing the overhead of thread switching, which makes Redis perform very well in terms of performance. At the same time, Redis also provides functions such as pipelines, publish and subscribe, and transactions, which can meet the concurrency needs in flash sale activities.

2. Overview of flash sale process

Before implementing Redis, let’s briefly introduce the flash sale process:

1. The user selects the product to be flash sale on the front-end page , and submit the order;
2. The system verifies whether the order submitted by the user is legal, such as whether the product inventory is sufficient, whether the user meets the participation conditions, etc.;
3. The system writes the order information into the database and returns it to the user Status in order processing;
4. The user continuously polls the order status during order processing until the order is completed.

During the flash sale process, the system needs to perform multiple verification and processing. The most critical part is to determine whether the product inventory is sufficient. This part needs to ensure the reliability and concurrency of the data.

3. Principle of flash sale implementation

1. Use Redis queue to store orders

During the flash sale activity, a large number of order requests will flood into the system at the same time. If traditional relationships are used Storage in a database will lead to excessive concurrency and too many database connections, thus reducing the performance and stability of the system.

In order to solve this problem, we can use a queue to store order information. Redis provides a List type data structure, which can be used as a queue implementation. By putting order information into the Redis queue, the system can quickly process a large number of order requests and process them on a first-come, first-served basis.

The following code shows how to use Redis queue to achieve flash sale:

$redis = new \Redis();
$redis->connect('127.0.0.1', 6379);
$key = 'seckill:orders';
$orderId = uniqid();
$data = [
    'user_id' => $userId,
    'product_id' => $productId,
    'order_id' => $orderId,
    'created_at' => time(),
];
$redis->lPush($key, json_encode($data));

2. Use Redis to pre-reduce inventory

During the flash sale activity, real-time monitoring of product inventory is required, otherwise Order processing may fail due to insufficient inventory. However, if every order is queried from the database for product inventory, it will increase the pressure on the database and reduce the concurrency performance of the system.

In order to solve this problem, we can use Redis's pre-stock reduction strategy. When users rush to buy, we first use the product inventory information in the Redis cache and update the cache information in real time. If the inventory has been reduced to 0, it will directly return the flash sale failure.

The following code shows how to use Redis to pre-reduce inventory:

$redis = new \Redis();
$redis->connect('127.0.0.1', 6379);
$productId = 'product:1001';
$stock = $redis->get('stock:'.$productId);
if ($stock > 0) {
    // 设置锁定时间
    $redis->incrBY('lock:'.$productId);
    // 预减库存
    $stock = $redis->decrBY('stock:'.$productId);
    // 判断库存是否足够
    if ($stock >= 0) {
        $orderId = uniqid();
        $data = [
            'user_id' => $userId,
            'product_id' => $productId,
            'order_id' => $orderId,
            'created_at' => time(),
        ];
        $redis->lPush('seckill:orders', json_encode($data));
    } else{
        // 增加库存
        $redis->incrBY('stock:'.$productId);
    }
}

3. Using Redis distributed lock

In the flash sale activity, although we use Redis queue and pre-reduce Inventory, but the system still needs to face a large number of concurrent requests. In these requests, there may be multiple users rushing to purchase the same product at the same time, which requires us to use distributed locks to ensure the reliability of the data.

The way to use Redis's distributed lock is very simple. At the beginning of the rush, we use Redis's SETNX operation to try to obtain the distributed lock. If the acquisition is successful, the inventory will be operated. After the operation is completed, the distribution will be released. style lock. If you fail to acquire the distributed lock, you need to wait for a while and try again.

The following code shows how to use Redis distributed lock:

$redis = new \Redis();
$redis->connect('127.0.0.1', 6379);
$productId = 'product:1001';
$lockKey = 'lock:'.$productId;
// 获取锁
$lock = $redis->SETNX($lockKey, 1);
if ($lock) {
    // 设置锁定时间
    $redis->expire($lockKey, 5);
    // 预减库存
    $stock = $redis->decrBY('stock:'.$productId);
    // 判断库存是否足够
    if ($stock >= 0) {
        $orderId = uniqid();
        $data = [
            'user_id' => $userId,
            'product_id' => $productId,
            'order_id' => $orderId,
            'created_at' => time(),
        ];
        $redis->lPush('seckill:orders', json_encode($data));
    } else{
        // 增加库存
        $redis->incrBY('stock:'.$productId);
    }
    // 释放锁
    $redis->del($lockKey);
}

4. Issues that need attention

1. Redis performance bottleneck

In the process of using Redis to implement flash sales, the main performance bottleneck is the bandwidth and responsiveness of the service where Redis is located. If the access pressure is too high, the response time of Redis will become longer, thus affecting the performance and stability of the entire system. Therefore, when implementing Redis flash sale, it is necessary to load test the system to check whether the performance and stability of the system meet the requirements.

2. Security Issues

Due to the high profit temptations in flash sale activities, some criminals may use various means to cheat. When using Redis to implement flash sales, necessary security precautions need to be taken, such as preventing malicious requests, repeating order submissions, performance limitations, etc.

3. Concurrency issues

The biggest problem in flash sale activities is concurrent request processing. If the system cannot effectively handle high concurrent requests, it may cause system crashes or slow access. When using Redis to implement flash sales, you need to consider the concurrency performance of the system to ensure that the system runs efficiently and stably.

Summarize:

This article introduces the principle and process of Redis implementing flash sales in PHP. Using Redis can effectively improve the system's responsiveness and reliability and ensure the success rate and fairness of flash sale activities. At the same time, when using Redis to implement flash sales, you need to pay attention to Redis's performance bottlenecks, security issues, and concurrency issues to ensure that the system runs efficiently and stably.

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